Outboard motor



March 1938. o. c. LINTHWAITE v 2,111,325

OUTBOARD MOTOR Filed June 4, l935 2 Sheets-Sheet 1 D mmvron; OWEN C. Lmmwmr" ATTORNEY V March 5, 1938- 0. c. LINTHWAITE ,1

OUTBOARD MOTOR Filed June 4, 1955 2 Sheets-Sheet 2 INVENTOR.

' Oman C. Lmmwanr ATTORNEY Patented Mar. 15, 1938 PATENT OFFICE OUTBOARD MOTOR Owen o. Linthwaite, South Bend, Ind., assignor to Bendix Products Corporation, South Bend, Ind., a corporation of Indiana Application June 4, 1935, Serial No. 24.898

6 Claims.

This invention relates to outboard motors for the propulsion of watercraft, and more particularly to a novel streamlined lower unit therefor.

In the operation of outboard motors, it has been found difflcult to provide suitable means for disposing of the exhaust gases from the engine in such a manner as to avoid noise without unnecessarily adding to the weight by employing a conventional type muffler as ordinarily used in lo connection with internal combustion engines in other arts.

It has also been found that to obtain maximum efficiency from a propeller, means must be provided to prevent the propeller from cavitating due to a depression in the fluid immediately adjacent and following the power transmitting housing, In the past this difficulty has been avoided by positioning a flat anticavitation plate to overlie the propeller and to avoid the forma- 'tion of a depression in the fluid adjacent the propeller.

An. object of this invention is therefore to provicle a novel stream-lined lower unit wherein an expansion chamber for exhaust gases is provided,

and means are employed to discharge the exhaust gases below the surfaceof the water at such an angle with respect to the propeller as to avoid in-- terference with the successful operation "of the propeller.

Another object of the-invention 15.110. provide'a' stream-lined lower unit-for an outboard motor so designed that it maybe formedby'ai'die-casting operation.

Another object of the'invention.is toprovide means for quietly and eflic'iently disposing of the exhaust gases of anoutboard motor so as to avoid back pressure on the engine and to minimize the energy required to discharge the gases.

Other objects and advantages of the present invention will appear in the following detailed description, taken in connection with the accompanying drawings, submitted for purposes of i1- lustration only, and not intended to define the scope of the invention, reference being had for that purpose to the subjoined claims.

'In the drawings, wherein similar reference characters refer to similar parts throughout the several views:

1f 1 Figure 1 is a view in elevation of an outboard 5 motor clamped to the transom of a boat;

tiongon an enlarged scale, of the lower portion of Figure 1;

Figure 3 .is an end elevation of Figure 2; 55 Figure 4 is a view on the line 4--4 of Figure 2;

cavitation plate 50, as shown. Figure 2 is an elevational view, partly in sec- Figure 5 is a view similar to Figure 2, showing a modified form of the invention;

Figure 6 is an end elevation of Figure 5;

Figure '7 is a view on' the line 1-1 of Figure 5;

Figure 8 is a view similar to Figure 2,showlng 5 a further modification of the invention;

Figure 9 is an end elevation of Figure 8;

Figure 10 is a view on the line Ill-l0 of Figure 8; 1

Figure 11 is a view similar to Figure 2, show- 10 ing a further modification of the invention;

Figure 12 is an end elevation of Figure 11;

Figure 13 is a view on the line l3-l3 of Figure 11; and

Figure 14 is a view similar to Figure-2, show- 15 operably connected with the upper housing section 22, is provided to turn the outboard motor assembly about a pivot point to effect steering operations'of the boat. Fuel is supplied for the operation of the engine from a fuel tank 32 posi-' -tioned below thefstream-lined hood 20.

. The upper housing'section .22 is'formedwith two longitudinal passages 34 and 3G. The lower housing section'24;isformed with two longitudi 'nal passages 38 and separated by a partition,

wall 42 which adds stiffness and strength'to the 35 lower housing 24. v The lower housing section 24 is provided with a propeller shaft housing 44, and a propeller protecting fln 46 designed to travel ahead of the propeller 48 to prevent the propeller 48 from strik- 40 ing an object which would damage the propeller.

An anti-cavitation plate 50 is provided to overlie the propeller 48 to prevent the formation of a depression in the fluid adjacent and following the lower housing section 24, and to prevent the 5 formation of air pockets in fluid through which the propeller is passing. A stream-lined fin 5|,

- to facilitate steering operations, is carried by the lower housing 24 immediately above the anti- Power from the engine is transmitted to the propeller 48 through an engine drive shaft 52 extending through the longitudinal passages 34 and 38 respectively of the upper and lower housing sections 22 and 24. 55

Exhaust gases from the engine are conducted from the engine to the longitudinal passage 36 in the upper housing 22 through a connection 81 interposed between the exhaust port oi the engine and the upper section of the housing 22. The longitudinal passage 36 is of progressively increasing cross sectional area downwardly, and communicates with the longitudinal passage 40 formed in the lower section 24. The longitudinal passage 40 provides a convenient expansion chamber for the exhaust gases to prevent back pressure on the engine cylinder. The exhaust gases are cooled as they travel downwardly through the longitudinal passages 36 and 40. The normal water level through which the lower unit 24 is passing is above the stream-lined fin 5| so that a chilling effect of the exhaust gases takes place to contract the gases. The volume of the gases is therefore decreased and back pressure is reduced to a minimum. The gases are discharged beneath the lower surface of the anti-cavitation plate 50 and above the propeller 48 through a rearwardly extending aperture 54, having a downwardly projecting lip 56. The lip 56 operates to form a section of reduced fluid pressures to the rear of the opening 54 thereby facilitating the flow of the exhaust gases from the passage 40 as the lower housing section 24 moves through the water.

It has been found from experiment that exhaust gases discharged above the propeller, but below the anti-cavitation plate in the manner described above will not cause the propeller to cavitate, and will not subject the engine to back pressure.

In operation when the engine is running, the

exhaust gases are discharged from the engine through the connector 31 to the passage 36 of the upper housing section 22, communicating with the passage 40 of the lower housing 24. The exhaust gases pass through a passageway of progressively increasing cross sectional area, and are subjected to a progressively decreasing temperature, causing them to contract as they movev downwardly, heat being conducted through the walls of the housing 24 to the water through which it is passing. The gases are drawn out through the opening 54, extending through the anti-cavitation plate 50 because of the movement of the fluid over the downwardly projecting lip 56.

Figures 5, 6, and 7 illustrate a modified form of the invention wherein the anti-cavitation plate 50 has a fiat lower surface designed to overlie the propeller 48. The exhaust gases are discharged from the passageway 40 through an opening 60, formed by an expansion of the fin 5| to form the rectangular shaped opening 60 above the anti-cavitation plate 50. The opening 60 is positioned to discharge the exhaust gases at a point intermediate the trailing edge of the anti-cavitation plate 50, and the forward edge thereof.

This embodiment of the invention is more particularly described in my copending application, Serial No. 2,085, filed January 16, 1935.

Figures 8, 9, and 10 illustrate an embodiment of the invention wherein a rectangular housing III is formed above the anti-cavitation plate 50, and is supported by a fin l2 projecting from the housing III to the anti-cavitation plate 50. The housing 10 is stream-lined into the fin 5| and forms an exhaust discharge opening 14 communicating with the longitudinal passageway 40, formed in the lower housing section 24. In this embodiment of the invention the housing 10' is preferably positioned forwardly of the trailing edge of the anti-cavitation plate ill as clearly shown in Figure 10.

Figures 11, 12, and 13 illustrate a further modified form of the invention wherein a stream-lined section III is formed by extending a portion of the housing 24 below the anti-cavitation plate 50. The stream-lined section is provided with an exhaust discharge opening 82 projecting below the anti-cavitation plate 50 and reinforced by a fin 84 projecting between the stream-lined section 80 and the anti-cavitation plate 50. In this embodiment, the exhaust gases are discharged below the anti-cavitation plate. It has been found by experiment that the arrangement shown herein will not cause the propeller 48 to cavitate.

Figure 14 shows a further modified form or the invention wherein the lower section 24 is cast or otherwise formed integral with the anti-cavitation plate 50, as in the other modifications previously discussed. The stream-lined fin and the exhaust outlet are not cast integral therewith, however, but are formed by a stamping adapted to be fixed to the lower unit by any suitable means such as a bolt 92 engaging a boss 94 to securely hold the stream-lined fin 90, and the exhaust passageway securely tothe lower houssimpler in view of the fact that the streamlined fin and the exhaust opening are not cast integral with the housing 24;

This application is a continuation-in-part of my co-pending application Serial No. 2,085, filed January 16, 1935.

While several illustrative embodiments of the invention have been illustrated and described, it is not my intention to limit the scope of the invention to the embodiments shown nor otherwise than by the terms of the following claims.

I claim:

1. In an outboard motor, a hollow housing, an anti-cavitation plate, a stream-1ined fin fixed to the housing and connected with the anti-cavitation plate by a reinforcing web extending from the mid-section of the fin to the plate, and-a rearwardly directed opening of rectangular cross section in the central portion of the trailing edge of the fin anterior to the trailing edge of the anticavitation plate and above said plate.

2. In an outboard motor, an internal combustion engine, a propeller to drivethe motor, a hollow stream-lined housing extending between the engine andthe propeller, means to conduct exhaust gases from the engine to the housing, an anti-cavitation plate carried by the housing and positioned to overlie the propeller, a portion of the housing being shaped to form a stream lined fin extending between the housing and the plate, the lower portion of the fin being extended laterally to form a single rectangular shaped rearwardly directed opening above the anticavitation plate to permit the escape of exhaust gases from the housing, and a reinforcing web extending longitudinally between the lower portion of the fin and the upper portion of the anticavitation plate.

3. In an outboard motor, an internal combustion engine, a propeller to drive the motor, a hollow stream-lined housing extending between the engine and the propeller, means to conduct exhaust gases from the engine to the housing, and an anti-cavitation plate carried by the housing and positioned to overlie the propeller, a portion of the housing being shaped to form a stream-lined fin extending between the housing and the plate, the lower portion of the fin being extended laterally to form a single rectangular shaped rearwardly disposed opening in the central portion of the fin discharging at a point intermediate the extreme ends of, the anti-cavitation plate and slightly above said plate to permit the escape of exhaust gases from the housing at a point below the surface of the water.

4. In an outboard motor, an internal combustion engine, a. propeller, a single hollow housing including two separate chambers extending between the engine and the propeller, means to conduct exhaust gases from the engine to one of the chambers of the housing, a drive shaft in the other of said chambers, an anti-cavitation plate carried .by the housing and positioned to overlie the propeller, a portion of the housing being shaped to form a stream-lined fin extending to the anti-cavitation plate, the central portion of the fin being extended laterally to form a single rectangular shaped rearwardly directed opening bounded by four walls separate and independent from the upper surface of the anti-cavitation plate, and reinforcing means betweenthe fin and l the anti-cavitation plate.

the anti-cavitation plate but below the normal water level.

6. In an outboard motor, an internal combustion engine, a water propeller, a housing extending between the engine and the propeller, means to conduct exhaust gases from the engine to the housing, an anti-cavitation plate carried by the housing, and means comprising a stream-lined fin including a rearwardly directed exhaust outlet supported by the housing above the plate, a reinforcing web between the fin and the anticavitation plate to support the fin to discharge exhaust gases from the housing below the normal water level but above the anti-cavitation plate.

OWENv C. LINTHWAITE. 

